Field of the Disclosure
The technology of the disclosure relates to coaxial cable connectors and, in particular, to a coaxial cable connector that provides integral radio frequency interference (RFI) shielding.
Technical Background
Coaxial cable connectors, such as type F connectors, are used to attach coaxial cable to another object or appliance, e.g., a television set, DVD player, modem or other electronic communication device having a terminal adapted to engage the connector. The terminal of the appliance includes an inner conductor and a surrounding outer conductor.
Coaxial cable includes a center conductor for transmitting a signal. The center conductor is surrounded by a dielectric material, and the dielectric material is surrounded by an outer conductor; this outer conductor may be in the form of a conductive foil and/or braided sheath. The outer conductor is typically maintained at ground potential to shield the signal transmitted by the center conductor from stray noise, and to maintain a continuous desired impedance over the signal path. The outer conductor is usually surrounded by a plastic cable jacket that electrically insulates, and mechanically protects, the outer conductor. Prior to installing a coaxial connector onto an end of the coaxial cable, the end of the coaxial cable is typically prepared by stripping off the end portion of the jacket to expose the end portion of the outer conductor. Similarly, it is common to strip off a portion of the dielectric to expose the end portion of the center conductor.
Coaxial cable connectors of the type known in the trade as “F connectors” often include a tubular post designed to slide over the dielectric material, and under the outer conductor of the coaxial cable, at the prepared end of the coaxial cable. If the outer conductor of the cable includes a braided sheath, then the exposed braided sheath is usually folded back over the cable jacket. The cable jacket and folded-back outer conductor extend generally around the outside of the tubular post and are typically received in an outer body of the connector; this outer body of the connector is often fixedly secured to the tubular post. A coupler is typically rotatably secured around the tubular post and includes an internally-threaded region for engaging external threads formed on the outer conductor of the appliance terminal.
When connecting the end of a coaxial cable to a terminal of a television set, equipment box, modem, computer or other appliance, it is important to achieve a reliable electrical connection between the outer conductor of the coaxial cable and the outer conductor of the appliance terminal. Typically, this goal is usually achieved by ensuring that the coupler of the connector is fully tightened over the connection port of the appliance. When fully tightened, the head of the tubular post of the connector directly engages the edge of the outer conductor of the appliance port, thereby making a direct electrical ground connection between the outer conductor of the appliance port and the tubular post; in turn, the tubular post is engaged with the outer conductor of the coaxial cable.
With the increased use of self-install kits provided to home owners by some CATV system operators has come a rise in customer complaints due to poor picture quality in video systems and/or poor data performance in computer/internet systems. Additionally, CATV system operators have found upstream data problems induced by entrance of unwanted radio frequency (“RF”) signals into their systems. Complaints of this nature result in CATV system operators having to send a technician to address the issue. Often times it is reported by the technician that the cause of the problem is due to a loose F connector fitting, sometimes as a result of inadequate installation of the self-install kit by the homeowner. An improperly installed or loose connector may result in poor signal transfer because there are discontinuities along the electrical path between the devices, resulting in ingress of undesired RF signals where RF energy from an external source or sources may enter the connector/cable arrangement causing a signal to noise ratio problem resulting in an unacceptable picture or data performance. In particular, RF signals may enter CATV systems from wireless devices, such as cell phones, computers and the like, especially in the 700-800 MHz transmitting range.
Many of the current state of the art F connectors rely on intimate contact between the F male connector interface and the F female connector interface. If, for some reason, the connector interfaces are allowed to pull apart from each other, such as in the case of a loose F male coupler, an interface “gap” may result. If not otherwise protected this gap can be a point of RF ingress as previously described.
A shield that completely surrounds or encloses a structure or device to protect it against RFI is typically referred to as a “Faraday cage.” However, providing such RFI shielding within given structures is complicated when the structure or device comprises moving parts, such as seen in a coaxial connector. Accordingly, creating a connector to act in a manner similar to a Faraday cage to prevent ingress and egress of RF signals can be especially challenging due to the necessary relative movement between connector components required to couple the connector to a related port. Relative movement of components due to mechanical clearances between the components can result in an ingress or egress path for unwanted RF signals and, further, can disrupt the electrical and mechanical communication between components necessary to provide a reliable ground path. The effort to shield and electrically ground a coaxial connector is further complicated when the connector is required to perform when improperly installed, i.e. not tightened to a corresponding port.
Electromagnetic interference (EMI) has been defined as undesired conducted or radiated electrical disturbances from an electrical or electronic apparatus, including transients, which can interfere with the operation of other electrical or electronic apparatus. Such disturbances can occur anywhere in the electromagnetic spectrum. Radio frequency interference (RFI) is often used interchangeably with electromagnetic interference, although it is more properly restricted to the radio frequency portion of the electromagnetic spectrum, usually defined as between 24 kilohertz (kHz) and 240 gigahertz (GHz). A shield is defined as a metallic or otherwise electrically conductive configuration inserted between a source of EMI/RFI and a desired area of protection. Such a shield may be provided to prevent electromagnetic energy from radiating from a source. Additionally, such a shield may prevent external electromagnetic energy from entering the shielded system. As a practical matter, such shields normally take the form of an electrically conductive housing which is electrically grounded. The energy of the EMI/RFI is thereby dissipated harmlessly to ground. Because EMI/RFI disrupts the operation of electronic components, such as integrated circuit (IC) chips, IC packages, hybrid components, and multi-chip modules, various methods have been used to contain EMI/RFI from electronic components. The most common method is to electrically ground a “can” that will cover the electronic components, to a substrate such as a printed wiring board. As is well known, a can is a shield that may be in the form of a conductive housing, a metallized cover, a small metal box, a perforated conductive case wherein spaces are arranged to minimize radiation over a given frequency band, or any other form of a conductive surface that surrounds electronic components. When the can is mounted on a substrate such that it completely surrounds and encloses the electronic components, it is often referred to as a Faraday Cage. Presently, there are two predominant methods to form a Faraday cage around electronic components for shielding use. A first method is to solder a can to a ground strip that surrounds electronic components on a printed wiring board (PWB). Although soldering a can provides excellent electrical properties, this method is often labor intensive. Also, a soldered can is difficult to remove if an electronic component needs to be re-worked. A second method is to mechanically secure a can, or other enclosure, with a suitable mechanical fastener, such as a plurality of screws or a clamp, for example. Typically, a conductive gasket material is usually attached to the bottom surface of a can to ensure good electrical contact with the ground strip on the PWB. Mechanically securing a can facilitates the re-work of electronic components, however, mechanical fasteners are bulky and occupy “valuable” space on a PWB.”
Coaxial cable connectors have attempted to address the above problems by incorporating a continuity member into the coaxial cable connector as a separate component. In this regard, FIG. 1 illustrates a conventional connector 1000 having a coupler 2000, a separate post 3000, a separate continuity member 4000, and a body 5000. In connector 1000 the separate continuity member 4000 is captured between post 3000 and body 5000 and contacts at least a portion of coupler 2000. Coupler 2000 is preferably made of metal such as brass and plated with a conductive material such as nickel. Post 3000 is preferably made of metal such as brass and plated with a conductive material such as tin. Separate conductive member 4000 is preferably made of metal such as phosphor bronze and plated with a conductive material such as tin. Body 5000 is preferably made of metal such as brass and plated with a conductive material such as nickel.